Simple metal oxides such as hematite and titania draw a tremendous interest as materials for photoelectrochemical (PEC) water splitting photoelectrodes to produce hydrogen as a clean and sustainable energy carrier. However, the high recombination rates of the photogenerated charges limits their application. Herein we report on highly efficient and stable composite titania-hematite photoanodes prepared by combining doped TiO2 nanoparticles with amorphous iron oxide and subsequent annealing. Studying the effect of various TiO2 doping by in-depth structural and chemical characterization, carried out through multiple technique approach, showed that doping of TiO2 allows subtle tuning of the phase composition, microstructure and surface topography of the photoanodes. When the photoanodes were prepared by combining Ta-doped TiO2 nanoparticles and amorphous iron oxide nanoparticles and subsequently annealed, remarkable photocurrents of up to 2.2 mA/cm2 at 1.23 V in 1M NaOH under 1.5 AM simulated solar illumination were obtained. The high photocurrents, which were traced back to Ta-doping, were elucidated by rutile-hematite heterojunction energetics, blocking layer formation and the doping. In addition to showing promises for a sustainable and cost-effective generation of an energy carrier, the presented strategies can also be expanded to other materials combinations opening doors for new modified semiconductors or heterojunction photoanodes.